<?php

// +----------------------------------------------------------------------

// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]

// +----------------------------------------------------------------------

// | Copyright (c) 2009 http://thinkphp.cn All rights reserved.

// +----------------------------------------------------------------------

// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )

// +----------------------------------------------------------------------

// | Author: liu21st <liu21st@gmail.com>

// +----------------------------------------------------------------------

namespace Think\Crypt\Driver;

/**

 * Base64 加密实现类

 */

class Think {



    /**

     * 加密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @param integer $expire 有效期（秒）     

     * @return string

     */

    public static function encrypt($data,$key,$expire=0) {

        $expire = sprintf('%010d', $expire ? $expire + time():0);

        $key  = md5($key);

        $data = base64_encode($expire.$data);

        $x    = 0;

        $len  = strlen($data);

        $l    = strlen($key);

        $char = $str    =   '';



        for ($i = 0; $i < $len; $i++) {

            if ($x == $l) $x = 0;

            $char .= substr($key, $x, 1);

            $x++;

        }



        for ($i = 0; $i < $len; $i++) {

            $str .= chr(ord(substr($data, $i, 1)) + (ord(substr($char, $i, 1)))%256);

        }

        return str_replace(array('+','/','='),array('-','_',''),base64_encode($str));

    }



    /**

     * 解密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @return string

     */

    public static function decrypt($data,$key) {

        $key    = md5($key);

        $data   = str_replace(array('-','_'),array('+','/'),$data);

        $mod4   = strlen($data) % 4;

        if ($mod4) {

           $data .= substr('====', $mod4);

        }

        $data   = base64_decode($data);



        $x      = 0;

        $len    = strlen($data);

        $l      = strlen($key);

        $char   = $str = '';



        for ($i = 0; $i < $len; $i++) {

            if ($x == $l) $x = 0;

            $char .= substr($key, $x, 1);

            $x++;

        }



        for ($i = 0; $i < $len; $i++) {

            if (ord(substr($data, $i, 1))<ord(substr($char, $i, 1))) {

                $str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));

            }else{

                $str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));

            }

        }

        $data   = base64_decode($str);

        $expire = substr($data,0,10);

        if($expire > 0 && $expire < time()) {

            return '';

        }

        $data   = substr($data,10);

        return $data;

    }

}